Hi I need help with these questions pls 8. How might gravitational waves be dete
ID: 1475390 • Letter: H
Question
Hi I need help with these questions pls
Explanation / Answer
Ans 8- Detection of gravitational waves
a. Weber bar-A simple device to detect the expected wave motion is called a Weber bar – a large, solid bar of metal isolated from outside vibrations. This type of instrument was the first type of gravitational-wave detector. Strains in space due to an incident gravitational wave excite the bar's resonant frequency and could thus be amplified to detectable levels.
eg-
MiniGRAIL is a spherical gravitational-wave antenna using this principle. It is based at Leiden University, consisting of an exactingly machined 1150 kg sphere cryogenically cooled to 20 mK.[15] The spherical configuration allows for equal sensitivity in all directions, and is somewhat experimentally simpler than larger linear devices requiring high vacuum. Events are detected by measuring deformation of the detector sphere. MiniGRAIL is highly sensitive in the 2–4 kHz range, suitable for detecting gravitational waves from rotating neutron star instabilities or small black hole mergers.
AURIGA is an ultracryogenic resonant bar gravitational wave detector based at INFN in Italy. It is based on a cylindrical bar detector. The AURIGA and LIGO teams have collaborated in joint observations.
b.A more sensitive detector uses laser interferometry to measure gravitational-wave induced motion between separated 'free' masses. This allows the masses to be separated by large distances (increasing the signal size); a further advantage is that it is sensitive to a wide range of frequencies (not just those near a resonance as is the case for Weber bars). Ground-based interferometers are now operational. Currently, the most sensitive is LIGO – the Laser Interferometer Gravitational Wave Observatory. LIGO has three detectors: one in Livingston, Louisiana; the other two (in the same vacuum tubes) at the Hanford site in Richland, Washington. Each consists of two light storage arms which are 2 to 4 kilometers in length. These are at 90 degree angles to each other, with the light passing through 1m diameter vacuum tubes running the entire 4 kilometers. A passing gravitational wave will slightly stretch one arm as it shortens the other. This is precisely the motion to which an interferometer is most sensitive.
answer 9 Einstein's theory of gravity (the general theory of relativity) predicts the Moon's orbit to within the accuracy of the laser ranging measurements
It is done by laser ranging, pointing them towards one or more of the retroreflectors that were left on the surface of the Moon by the Apollo landers, in what is known as the Lunar Laser Ranging Experiment. Since they are laid on the Moon's near side that is always pointed towards the Earth, these retroreflectors are available for measurements to any properly equipped researcher, no matter which country they're from.
By measuring the time it takes for the light to reflect back, we can infer distance by simply multiplying the c (speed of light in vacuum) with the time taken between the light signal being transmitted and received and then dividing all of it by two to get a single leg of the distance.
Answer 10 Einstein wrote that the speed of light does not depend on the speed of the object emitting the light. To prove this, Einstein referred to De Sitter’s observation of the binary stars, which are two stars that are orbiting each other. De Sitter concluded that if the speed of light were dependant on the speed of the star, then the light emitted from the star as it is traveling towards us would eventually catch up to the light that was emitted from the same star when it was traveling away from us. That logic is incorrect since relative to the binary stars, they are not moving and we are orbiting the binary stars. By viewing the stars as motionless, it becomes clear that while we orbit the binary stars, we are running into the light of one star as we are running away from the light from the other star. Relative to the binary stars, their light is not approaching us at different speeds; we are approaching the light at different speeds. This proves that the speed of light can be based off the speed of the star without disturbing our perceptual view of the orbits.
Answer 11 Light travels in waves, and, like sound, can be slowed depending on what it is traveling through. Nothing can outpace light in a vacuum. However, if a region contains any matter, even dust, light can bend when it comes in contact with the particles, which results in a decrease in speed.